2020 Volume 62 Pages 85-94
We investigated the toxicity of several insecticides to Arrhenophagus albitibiae Girault (Hymenoptera: Encyrtidae) parasitizing white peach scale, Pseudaulacaspis pentagona (Targioni-Tozettii) (Hemiptera: Diaspididae), in tea crops using three different laboratory assay methods. We checked the toxicity of 25 pesticides using the dry-film method and of 63 pesticides (55 insecticides + eight fungicides) using the contact method by spraying the pesticides on the tea branches. We also tested the toxic effect of 43 pesticides (40 insecticides and three fungicides) on the emergence of parasitoid pupae by dipping tea branches with the pupae into pesticide liquid. Moreover, we investigated the susceptibility of the parasitoid adults to four types of neonicotinoids using the contact method. The results of the dry-film test showed that many pesticides were more than moderately harmful to A. albitibiae, whereas organophosphate, pyrethroid, and avamectin/milbemycin insecticides were seriously harmful to A. albitibiae. The results of the contact test showed that most of the organophosphate, pyrethroids, spinosad, pyridaben, and milbemectin insecticides were seriously or moderately harmful, whereas insect growth regulators (IGRs), diamides, most acaricides, most other groups of insecticides (IRAC code: 2B, 9B, 11A, 12A, 13, 12A, 21A) and fungicides were only slightly harmful or not harmful to A. albitibiae. The toxicity test regarding the emergence of the parasitoid showed that only some organophosphates and pyrethroids were slightly harmful. The LC50 values of the A. albitibiae adults under the four types of neonicotinoids were 5.6 ppm, 37.5 ppm, 176.1 ppm, and 177.7 ppm for clothianidin, imidacloprid, thiacloprid, and acetamiprid, respectively.
